Up to now, the electric contacting of the heating element of such an electric heater, which is usually designed as a resistance wire and is sometimes called a heating wire or heating conductor as well, is usually implemented in the following ways:
First, an attempt can be made to work with crimp connectors. This is problematic—especially when a connection shall be made in the interior of the jacket of an electric heater—on the one hand, with manual production with regard to the desired process safety, since three parts have to be positioned together exactly at the same time, and, on the other hand, with regard to achieving a compact design, since a connection made according to the crimping instructions usually leads to applying the crimped sleeve in the direction, in which it is not pressed together.
On the one hand, it is known to provide a ceramic, especially porous, component with at least one hole, in which an end section of the electric heating element is crimped with a connecting wire in an overlapping manner. However, this solution almost always means that the structural space needed is enlarged, because besides the hole, which electric heating element and connecting wire must accommodate, a wall thickness must be provided that withstands the mechanical stresses occurring and guarantees the necessary electric insulation.
On the other hand, it is known that a connecting wire is butt-jointed or firmly welded at the heating element in an overlapping manner. However, this is especially not a satisfactory solution if one has to work with high currents and/or small resistances and/or relatively low voltages for operating the electric heater, such that transfer or contact resistances can be made highly noticeable with regard to the process safety achieved. On the one hand, differences in weight ratios of connecting wires and electric heating element have a negative effect on the quality of the resulting welded connection.
This approach also requires an exact positioning of the welding spot, since, especially in plasma or microplasma welding, the slightest deviations, especially a cross-sectional reduction of the weld, may have a negative effect on the electric contacting, and a slight slipping or unsteadiness of the parts to be connected in relation to one another during curing of the melt may already lead to an inhomogeneous melt, which likewise means contact problems. Such an unsteadiness may also force a subsequent mechanical alignment and/or calibration of the welded connection for achieving the marginal conditions regarding the space, which may mean further contact problems.
Finally, an application of material to the weld joint cannot always be avoided even when providing welded connections, which increases the space needed for installation.